So everyone knows that since the rise of Defog users Starmie's niche as arguably the best spinner in the game has been devalued to the point where, for the first time in fifteen years, Starmie dropped to UU. But I feel Starmie has another niche, as a rather unpredictable and underestimated attacker with utility in the forms of Recover, Trick, Rapid Spin, and Natural Cure. Here's a Starmie set I've been running to relatively good effect.
Starmie @ Choice Specs
Timid - Analytic
252 Speed, 252 Sp. Atk, 4 Sp. Def
-Hydro Pump
-Thunderbolt
-Ice Beam
-Trick
Analytic may seem strange on a Pokemon with 115 base Speed, but it activates if the opponent switches as well, seriously punishing switchins by making them eat a stupidly strong Hydro Pump. Come in on a Heatran or a Garchomp, or something slower that will fear Starmie's coverage and punish the switchin. Trick ditches the Specs and can cripple Chansey, Ferrothorn, Suicune, etc. Even if the opponent doesn't switch, Starmie's decent base 100 Sp. Atk backed by Specs will still put a dent in whatever is staying in. Additionally, Starmie's Speed tier puts it ahead of Gengar, Mega Gallade, Mega Metagross, etc.